Volume 2, Number 3
Aug 1989

101-Year-Old Observation on Alum

It has often been stated that the cause of paper becoming brittle
or tender is to be found in the presence of alum or aluminum sulfate
in the paper. The author's observations, extending over 10 years,
tend to the conclusion that neutral or basic aluminum sulfate
exercises no decomposing influence at ordinary temperatures on
paper, whether size be present or not, but that aluminum sulfate has
a strongly caustic action if chlorides, such as those of sodium or
calcium, be present, especially at higher temperatures. In this
case an injurious action on the paper arises from the formation of
aluminum chloride or free hydrochloric acid, which act by
abstracting hydrogen, or the elements of water, from the cellular
substance.